The present invention relates to a new thermally protective liner which can be used as an inner, outer or intermediate liner in protective garments designed to protect the wearer from hazardous environmental conditions. More particularly, the present invention relates to a new thermally protective liner which (i) is extremely thin, perspiration permeable, and breathable; (ii) provides the wearer with the best protection possible from high external heat by supplying a significantly higher Thermal Protective Performance value in a thinner format; and (iii) provides the suit designer with the ability to design specify the water vapor ventilation, the thermal protective performance (TPP), the thickness, and the weight, thereby rendering protective garments lighter, thinner and more efficacious than those currently available.
Protective garments are designed to shield the wearer from a variety of environmental hazards such as heat and fire. Fire fighter garments as well as garments worn by individuals working on high voltage power lines, are representative of such garments.
Fire, in particular, is a very dangerous element. It moves and spreads quickly, putting lives and property in danger in a very short period of time; including the very lives of those fighting the fire. Consequently, fire fighters must themselves be properly protected, while at the same time be provided with tools and garments that allow them to move with tremendous speed and alacrity, while simultaneously allowing them to maintain their strength and stamina.
Accordingly, the qualities most desirable in fire fighters"" garments as well as other thermal control garments are minimum weight, maximum flexibility, high thermal protection, vapor ventilation, tensile strength and minimum water absorption.
Thermally protective garments and more particularly, fire fighters"" garments basically comprise three layers: (a) an outer shell, (b) an inner liner, including a moisture barrier, and (c) a thermally protective liner; traditionally insulation.
The outer shell basically consists of a fabric of aramid fibers such as NOMEX(copyright), KEVLAR(copyright) (both registered trademarks of E. I. DuPont) or a NOMEX(copyright)/KEVLAR(copyright) blend which provides resistance to abrasion, some thermal resistance, and structural integrity.
The moisture barrier, which usually is located right next to the outer shell, basically consists of a membrane of GORETEX(copyright) (a registered trademark of W. L. Gore and Associates, Inc.) material. The GORETEX(copyright) material has micropores, which permit the transport of moisture vapor, thereby allowing the perspiration moisture vapor of the wearer to escape outwardly; but which are sufficiently small to prevent liquid moisture from passing through to the wearer from the outside.
Finally, the thermally protective liner comprises an insulation layer of spun carbon, NOMEX, KEVLAR fibers, or a batting of any combination of such fibers, often quilted to a lightweight NOMEX face cloth. The batting of the thermal barrier traps air and possesses sufficient loft to provide the necessary thermal resistance, while the face cloth provides resistance to abrasion of the thermal liner by the wearer, and provides structural integrity and tensile strength to the insulation layer.
The prior art has many disadvantage and drawbacks. Specifically, in order to increase the Thermal Protective Performance (TPP) value of the prior art, one would have to use a thicker layer of insulation. In so doing, the wearer of the prior art would experience an increased weight, increased xe2x80x9chobblingxe2x80x9d effect, a decreased mobility and a decreased drapeability and a diminished flexibility. Furthermore, as a result to the increased thickness of the insulation, there will be an increase in the capillary action, which in turn will result in the absorption of water vapor. This absorption of water vapor will make the suit heavier and less wearable; increase fatigue; and under certain circumstances or rare high heat, the excess water trapped in the insulation could adversely affect the insulation""s Thermal Protective Performance value.
In summary therefore, the additional bulk and loft provided by the fabric thermal liner of the prior art inhibits the freedom of movement of the wearer, producing a xe2x80x9chobbling effectxe2x80x9d, thereby increasing the stress imposed on the wearer in a situation requiring high activity and accelerating the onset of the wearer""s fatigue. This xe2x80x9chobbling effectxe2x80x9d becomes particularly pronounced when the fabric thermal liners are excessively thick.
The replacement of this thermal liner, as described above with an Aldridge et. al. U.S. Pat. No. 5,136,723 open mesh insulation thermal barrier will still impede the transport of moisture vapor. Nor will the replacement of this thermal liner with the Aldridge U.S. Pat. No. 5,697,101 apertured closed cell foam material, will resolve the above referenced disadvantages and drawbacks.
First, closed-cell foam is stiff. Accordingly, even at minimum thicknesses a closed-cell foam thermal liner will be bulky, and unmanageable. Thus, the use of a closed-cell foam thermal liner in thermal protective garments, such as fire fighters"" garments will continue to produce the xe2x80x9chobbling effectxe2x80x9d produced by bulkier materials, and to contribute to the stress and fatigue of the wearer.
Second, in order for perspiration to escape to the outside, the closed-cell foam thermal liner must be perforated by as much as 45% of the total surface area of the liner. When 45% of the area is perforated, it leaves only 55% of effective closed-cell foam insulation for the liner. This means that as a function of the loss of 45% insulation, the TPP of said thermal liner drops dramatically. As the TPP drops, it limits the thinness of the closed-cell foam thermal liner and mandates the formation of a thicker closed-cell foam thermal liner to compensate for the loss of TPP.
Since, the closed-cell foam thermal liner will have to be made thicker to compensate for the loss of TPP, it will be bulkier and less flexible if it is to be used for protection from extreme heat exposure. Accordingly, it will have minimum use in situations where the wearer still needs flexible drapeable garments but more than adequate protection from extreme heat. Furthermore, it will fail miserably in reducing the xe2x80x9chobbling effectxe2x80x9d usually associated with thermal protective garments.
It is, therefore, an object of the present invention to provide a flexible, drapeable thermally protective liner capable of significantly reducing the xe2x80x9chobbling effectxe2x80x9d produced by bulkier thermal liner materials, thereby diminishing the stress and fatigue on the wearer.
It is another object of the present invention to provide a very thin thermally protective liner capable of meeting and exceeding the National Fire Protection Association""s (hereinafter xe2x80x9cN.F.P.A.xe2x80x9d) requirements for sufficient thermal insulation and protection, in extreme high heat conditions.
It is another object of the present invention to provide a very thin thermally protective, endothermic liner capable of both protecting the wearer and remaining stable and effective under extreme environmental situations.
It is another object of the present invention to provide an endothermic flexible material suitable for apparel and clothing having the ability to absorb high amounts of heat and protecting the wearer of such clothing when exposed to extreme environments of heat.
It is another object of the present invention to provide an endothermic material for applications requiring a material to be thin, flexible, drapeable, conformable, breathable, lightweight and comfortable, while simultaneously protecting and insulating against high heat environments.
It is another object of the invention to provide a thermally protective liner and/or endothermic flexible material/fabric which can be appropriately and easily modified to meet design specifications as determined by specific applications.
According to the present invention there is provided a thinner, lighter, flexible, drapeable, conformable, breathable, and more comfortable thermally protective liner for use in thermally protective garments capable of replacing the currently available thermal liners and capable of providing higher TPP values. The inventive thermal liner comprises a PCEA i.e xe2x80x9cPxe2x80x9dolymer xe2x80x9cCxe2x80x9dontaining an xe2x80x9cExe2x80x9dndothermic xe2x80x9cAxe2x80x9dgentxe2x80x9d, which is chemically and mechanically processed to form a very thin film, a composite film, a cloth made from PCEA which is either spun, woven, knitted or made from non-woven means or a PCEA fiber/insulation composite, wherein the PCEA fibers are integrated with insulation or other protective fibers. The PCEA, in turn, comprises a polymer and an endothermic agent dispersed, distributed and suspended within the polymer, in design specific concentrations.
The inventive thermally protective liner makes use of the PCEA""s suspended endothermic agent""s own inherent thermodynamic, physical and chemical properties i.e. its latent heats of fusion, hydration, formation, decomposition, vaporization, sublimation, and/or allotropic and phase change reactions, to absorb massive amounts of heat from the surrounding adverse environment. This absorption of heat is what ends up protecting the wearer of the liner-bearing garment from the extreme heat producing environment.
When the thermally protective liner in the thermoprotective garments comprises a thin PCEA film and breathability of the garments is an issue, then it must be perforated with apertures of variable dimensions. These apertures can include holes. Typically, the total perforation area is 5%-35% of the total surface area of the PCEA layer; and preferably, the perforation area is 20% of the total surface area of the PCEA layer.
In an alternate embodiment of the thermally protective liner, the PCEA layer is a composite film. The composite PCEA film is formed as follows: the PCEA is formulated and deposited on a fabric backing, polymer backing, plastic backing, metalized plastic backing, graphite fabric backing, or any combination thereof. It is deposited in discrete, defined areas, which can be any shape possible and which allow narrow paths to run between them. The narrow paths that run between these defined areas are substantially free of the PCEA and consist of plain polymer, plastic, or fabric matrix backing. Multiple apertures are provided along the narrow paths, which while substantially preventing any capillary leakage of the endothermic agent from the PCEA areas improve the sealing in of the endothermic agent, and provide a path for ventilating water vapor through liner. Simultaneously, such pathways will also improve the drapeability and flexibility of the liner.
Where the thermally protective liner is a cloth made from PCEA which is either spun, woven, knitted or made from non-woven means or a PCEA fiber/insulation composite, wherein the PCEA fibers are integrated with insulation or other protective fibers breathability of the PCEA layer is moot, as apertures are inherent to the methods of preparation of the cloth, or forming of the insulation/batting.
Irrespective of what form the inventive thermally protective liner will take i.e. film, cloth, batting or insulation, it will render thermally protective garments much thinner than ever before, yet better capable of satisfying and exceeding the thermal insulation standards of the National Fire Protection Association. The characteristics that provide these advantages are as follows: First, by virtue of the chemistry of the endothermic agents, in the xe2x80x9cpxe2x80x9dolymer xe2x80x9ccxe2x80x9dontaining xe2x80x9cexe2x80x9dndothermic xe2x80x9caxe2x80x9dgent i.e., in the PCEA, the thermally protective liner provides the best and most effective heat absorbing and heat shielding properties when compared to previous insulating materials. In fact, as will be shown below, a PCEA thermally protective liner limits the rate of temperature rise better than any other thermal barrier liner ever used in fire fighters"" garments.
Second, the thermally protective liner of the present invention is truly more dimensionally stable and uniform in thickness than any comparable thermal insulation of prior art. Thus, a sheet of the present liner can be made thinner than standard Aralite batting, and still meet and exceed the minimum overall N.F.P.A requirements for thermally protective liners.
Third, the inventive thermal liner itself, does not absorb any water from either the outside or from the wearer. Accordingly, it may be used in conjunction with a much thinner batting insulation or face cloth, which reduces dramatically the water retention of the entire garment.
Thus, the reduction of the conventional batting insulation or face cloth together with the inventive, thinner more thermally protective liner ultimately provides a thermally controlling garment whose overall size and bulk is reduced significantly; whose xe2x80x9chobbling effectxe2x80x9d is minimized dramatically; whose wearer""s stress and fatigue is reduced remarkably; whose donning and doffing by the wearer is greatly facilitated; and whose thermally protective performance to weight and thickness ratio is maximizable.
The aforementioned objects, as well as others, will be found in detail in the following written disclosure.